Gas tonometer



FIG. 1 is a front three quarter perspective view of a gas tonometershowing our new design;

FIG. 2 is a right side elevational view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a rear elevational view thereof; and

FIG. 6 is a top plan view thereof.

The ornamental design for a gas tonometer, substantially as shown.